Just wondering if anyone would know why barrells are rifled? I believe this is to make them spin and therefore more accuarate? However need it in a bit more detail, attemping to technical presenation on the new non rifled barrel of the Challenger 2. Any help, links etc would be great! Thanks

Its all about stabilising the projectile. Length and weight of projectile is directly related to the rate of twist required (1turn in 12 inch etc) some rounds going at up to 4000rpm will be rotating at IRO 80K RPM. Do a search on the internet and you should pull up plenty of information.

Seems a stunningly basic question, however I spose that's only because us Armrs are damn good chaps ....

Rifling was introduced to small arms barrels when it was found that imparting some degree of spin to the projectile produced greater accuracy over greater ranges. The same idea was later scaled up for use in gunnery (cannon/artillery) and subsequently mobile mounted gunnery (tank). For some years though there has been greater development in shifting the stabilising 'cause' from the barrel to the projectile, as different projectile types can benefit from different stabilising methods/rotation rates. Thus a smooth bore gun might achieve better performance with a greater range of projectile types than a rifled gun.
Such examples of basic types might be shorter range, lower velocity HE rounds might be stabilised by flip out fins, whereas longer range, high velocity kinetic AP already have fins as part of the penetrator (APFSDS). The smooth bore would also permit the wider use of tank fired missile munitions along the lines of the old US Copperhead system.

I have a nasty feeling I might actually have been paying attention at SEME